The pollution of the environment with harmful substances affects the quality of life and optionally also the health of persons staying in this environment and moreover has consequences with regard to the preservability of the respective flora and fauna. This realization results, on the one hand, in the necessity to develop processes for assessing the environmental quality parameters for relevant harmful substances and to employ said processes regularly and continuously, respectively, depending on a risk assessment in order to, on the one hand, monitor the observance of limiting values which are stipulated by laws or guidelines and, on the other hand, identify potentials for measures which allow the attainment of a target value. Thereby, it must be considered that the pollutant concentrations vary spatially and temporally.
Against this background, environmental quality monitoring networks have been established worldwide in the past 30 years which perform the required measurements using the available technology. The processes and assessment methods to be used for this purpose are standardized in detail for many areas of application, which, on the one hand, is indeed useful for the comparability of the assessment results but, on the other hand, inhibits the implementation of new processes and groundbreaking technology. In the field of air quality measurement, the measuring methods employed in the instruments have, for example, remained basically unchanged since the early 70ies.
The findings from the data obtained in said time period in comparison to medical data, i.e., the epidemiological research with respect to the impact of atmospheric pollutants, leads to the determination of limiting values and target values for the individual harmful substances. Thereby, it is necessary to distinguish between limiting values which must not be exceeded in the annual average and such values which must entail measures also in case of a short-term exceedance, i.e., alarm thresholds. Due to the technological advancement on the emitters' side (for example, by using catalytic converter technology or low thionated fuels) but also due to a shift in the composition of the parent population of all emitters (e.g., an increasing proportion of vehicles with Diesel drive units or a higher amount of solid biomass fuels), the focal points of the required assessments can shift over time, which is well displayed, on the one hand, by the decline in the significance of sulfur dioxide monitoring and, on the other hand, by the significant increase in the significance of an assessment of the concentration of fine dust (PM10). Thus, the respective monitoring systems must exhibit an appropriate flexibility in terms of the diversity of harmful substances to be detected.
In recent years, the attention of authorities in charge of preserving air quality has concentrated more and more on so-called “hot spots”, i.e., areas in which, due to specific conditions such as a high concentration of emitters, specific meteorological positions or the like, limiting values and, occasionally, alarm thresholds are exceeded to an increased degree. Such areas can either be developed as permanent hot spots, for example, at extremely busy traffic junctions, or can arise temporarily, for example, during the implementation of large-scale building projects.
The prior art is characterized by a dichotomic situation:
On the one hand, automated measuring stations which measure with a high temporal resolution and detect a multitude of harmful substances are used. These stations usually consist of container-like air-conditioned buildings or constructions which protect the laboratory equipment installed in their interior (per harmful substance, there is typically one analytical instrument comprising a mains supply, a sensor, signal processing, internal measured-value calculation, a display and an operating element as well as interfaces for communication with a master computer) from the elements and from access by unqualified persons. Appropriate sampling systems conforming to standards as well as instruments for the temporally synchronized detection of meteorological data (rain, temperature, wind force and direction) complete the measuring setup. Typically, such a station also contains a local data acquisition unit (front-end processor, logger or the like) which then transfers the measured values via long-distance data transmission to the centre of the measuring network where the analysis is performed using specialized software. As can be understood from the above description, these stations are complex installations which, due to their dimensions and the supply systems required for the operation as well as the investments associated therewith, typically cover areas of several to several hundred square kilometres per station and thus are unsuitable for the—at best temporary—use at a plurality of hot spots.
On the other hand, there are passive or diffusion collectors functioning according to Fick's law of diffusion which are limited in terms of the detected number of different harmful substances according to the number and type of the diffusion collectors installed per collecting point, wherein a single diffusion collector is typically suitable only for one harmful substance while, however, in specific cases, up to three harmful substances can be detected simultaneously. Therefore, as a result of the small size of the individual collectors—typically, they are small tubes having a maximum length of several 100 mm and a diameter of typically 10-20 mm—a measuring arrangement comprising 4 diffusion collectors of this kind corresponds, with regard to its size, to typical nest boxes for singing birds and, in terms of the compactness of the dimensions, is thus suitable for locally highly resolved measurements. However, the typical averaging time, i.e., the time span for which an individual measured value can be determined, is 7 to 14 days for all diffusion collectors. Since, in addition, said collectors must also be taken to a laboratory for analysis and must be evaluated there by desorption and further analysis methods, assessments of the pollutant concentration in the measuring range cannot be provided in real time. During the measurement, there is also no detection of local meteorological conditions.
Self-sufficient analyzers are used in the conventional technology. This has historical as well as practical reasons. The historical reasons lie in the ongoing development of analyzers for the harmful substances which are relevant at a particular time.
Each new harmful substance has been given a new analyzer which, in turn, has been added to a measurement rack in order to be able to measure a new harmful substance in the measuring station.
Normally, such analyzers measure only one harmful substance per analyzer. This has also a historical background which is basically accounted for by the performance of the electronics. A typical 19″ measuring instrument was filled to capacity by the required electronic components with regard to measurement and control technology as well as the power supply unit, the pump and the actual measuring sensor, the display and the control device. In spite of that, the devices were extremely sensitive to variations in temperature and air humidity, which is typical of laboratory equipment. Therefore, the devices were integrated in air-conditioned measurement rooms.
Still today, the standards for air quality systems are based on this architecture.
Thus, in the normal case, each analyzer for gaseous atmospheric pollutants consists of sample ducts internal to the measuring device which receive the sample material (test gas) from a central sampling, which, in turn, is specified in terms of shape, size and design according to standards, and, first of all, convey the same to a particle filter which protects the usually optical measuring systems from soiling by filtering out dust. Thereupon, the duct leads to a sensor. The actual measurement principles of the sensor are physical in nature and have remained unchanged for decades. They are also laid down in the standard as so-called reference methods.
In a measuring station which, due to the necessary manual interventions, must be designed such that said interventions can be carried out in accordance with safety regulations and that the analyzers are protected from unauthorized outside access, all analyzers in at least one measurement rack are usually mounted on top of each other in an assembly form as common in the industrial process technology. All devices are supplied via a switch cabinet embedded in the measuring station.
The analyzers are designed for set-up in interior spaces and react to variations in ambient conditions (air temperature and humidity) mostly with measured value variations, in case of more extreme deviations also with an equipment failure.
In order to maintain the quality of the measurement, the room temperature and air humidity must therefore be kept within particular variation ranges at the known measuring stations. For this purpose, an air volume resulting from the dimension of the station is used on the one hand, which air volume serves as a thermal mass and keeps the same, in terms of the key data air temperature and humidity, within the range which is required for the desired measuring accuracy, using an appropriately dimensioned conventional air-conditioning system.
It is known that the power required for a proper operation of the measuring system thereby depends on the size of the modified volume, the heat transition values of the boundary walls, the outside conditions as well as the number and capacity of consumers producing waste heat. The latter consist, on the one hand, of the waste heat of auxiliary units such as power transformers, pumps and the like and, on the other hand, of specific sources of waste heat such as, for example, infrared emitters or heated catalysts, which result from the applied measuring methods.
For common measuring stations corresponding to the prior art, the requirement of energy typically amounts to several kW as a result of the installation sizes and the high number of sources of waste heat so that, usually, power supply terminals must also be provided for the operation.
A central sampling unit comprising a main pump provides for an adequate flow of test material from which the analyzers in turn withdraw their test gas.
Normally, data pooling is effected by means of a data logger with an integral microprocessor which requests the data as a master from the measuring instruments and stores them appropriately along with a time value. Thereby, only fully calculated measured values of the individual analyzers are available for storage. In some embodiments, a spreadsheet with zero and span information which allows an assessment of measuring results can be filed in addition. Today, most data loggers are provided with local mass storage such as, e.g., a hard disk on which the queried measured value tables can be stored temporarily.
Via a modem, said tables are then sent via long-distance data transmission to a master computer in the measuring centre according to a preprogrammed (time-dependent) pattern. Normally, the statistical evaluation, e.g., in daily average values or the like, is conducted there and is made available to the public from there. It can also be made available to the public by transmission to a web server.